Electrical protecting device



Sgpt. 12, 1939. R. D. NELSON ELECTRICAL PROTECTING DEVICE Filed July 30, 1937 2 Sheets-Sheet l INVENTOR Sept. 12, 1939.

R. D. NELSON ELECTRICAL PROTECTING DEVICE' 2 Sheets-Sheet 2 INVENTOR. Palm/v05. A/aso/v A ORNEY.

Filed July 30, 1937 Patented Sept. 12, 1939 2,172,640

UNITED STATES PATENT OFFICEv 2,172,849 mc'ralcar. morac'rmo nav ca Rolland 1). Nelson, Milwaukee, Wis assignor to line Material Company, South Milwaukee, Win, a corporation of Delaware Application July 30, 1937, Serial No. 156,539 15 Claims. (01. 115-294) This invention relates to electrical protecting invention applied to a single bushing transformer devices. construction. v Objects of this invention are to provide a pro- Figure 2 is an enlarged sectional view through tecting device which is adapted to protect a the protective unit or follow-through current intransformer, electrical switch and transmission terrupting member. 5

line, or any other electrical instrumentality, and Figure 3 is a fragmentary view of the upper the invention is particularly directed to means p rt o t e trenSfOrmel' With P8118 broken which protect against a sudden surge on the line awaywhile still preventing the follow-through current ure 4 is a; plan view of the top 01 1lhe trans- 0 after the surge has passed without requiring the 101111811 use of any auxiliary apparatus. Figure 5 shows the invention as applied to a Additionally, in devices of this type diillculty double vbushing r n ormer having two sp has been encountered due to the fact that birds 8 9 frequently bridge or short-circuit the gap and Figure 6 shows the invention as applied to a is thus start an are which if not interrupted, will transformer or other electrical device in which a cause damage. It is, therefore, a further object portion 37 0f the casing is conductingof this invention to provide a construction which Figure 7 shows the invention as applied to an overcomes this defect due to the bridging of the oil switch. gaps by birds so that although a bird may alight Flgureii s w t ve t n pp to a d son the apparatus and temporarily bridge the gap, connec ing switch. 20 the fault is immediately burned out and follow- Figure 9 Shows e invention pp to through current is prevented, as in the case of a transmission linelightning surge. Referring to Figures 1 to 4 of the drawings,

Further objects are to provide a construction it will be seen that a rural type single bushing 5 which may be applied to an electrical instruransformer has been shown as provided with mentality equipped eith r with one or more a casing I formed of conducting material, which spark gaps, the apparatus being so constructed obviously may be of any suitable shape and may that cooperative action between either gap a d be provided with a cover portion, as shown in the valve material or negative resistance mate- F gure 3. The casing is provided with an inao rial is obtained, the construction permitting the sulatlns bushing 2 through wh c e ve h so use of a single member provided with the valve nsion lead 3 is carried. For example, the inmaterial for either one or a plurality of spark s ator 2 may carry an upper terminal member 8 -D l which, by means of the connector 5, joins the Further objects are to provide a construction high tension lead 3.

in which where a conducting case or conducting A spark gap is provided between the casing i :5 portion or member is employed and separated and the high tension lead 3 and may consist of from the high voltage line by means of spark an upwardly projecting rod 15 positioned directly gaps, the conducting portion itself may form a below the downwardly turned rod or spark gap part of the ground discharge circuit, valve mafinger I supported from the terminal 4.

terial being provided between such conducting A fuse link 8 is interposed between the live side 40 portion and the ground and the construction fur- 0f the primary 9 of the transformer and the high theiinsuring protection e n und t t tension lead 3, as shown diagrammatically in ly adverse condition where a portion of the high Figure e other e O -Prim 3 b n tension line becomes grounded to the conducting connected to the G u neutral W which portion of the apparatus, the valv t i tends to the grounded or neutral terminal ll of -qulckly failing and causing a fuse or other device the secondary The uter ends of the 596011- to open the circuit and thus protect th t dary are connected to the terminals l3. Suitable This feature, however, avoids any chance of insulating bushings H are interposed between dangerous potential being permanently built u the neutral and the outer sides of the secondary between the ground and the conducting portion I! and the casing I. It is customary t on ect of the apparatus. the grounded side of the high tension line indi- Embodiments of the invention are shown in the cated at 8' to the neutral terminal ll. accompanying drawings, in which: It will be seen, therefore, that the neutral is not Figure 1 is a di view showing t e directly grounded to the casing. However, a u

valve member indicatedgenerally at A, is interposed between the neutral and the transformer casing. This valve membermay employ valve material, such as silicon carbide, which is commonly known as granulon, or any other suitable material. The material has a negative resistance characteristic and is indicated by the reference character IS in Figure 2. It may be carried within an insulating cylinder I6 provided with upper and lower annular flanges I1 and I8 about which the inwardly turned flanges l9 and 2B of the upper cap 2| and the lower cap 22 may be spun, preferably rubber or other sealing material being interposed between the caps and the ends of the cylinder, as indicated in Figure 2.

A lower supporting member and conductor 23 is brazed, soldered, or otherwise secured to the lower cap 22 and an upper conductor and supporting member 24 is similarly brazed, soldered, or otherwise secured to the upper cap 2|. The members 23 and 24 may be relatively rigid bars. The lower combined conductor and support 23 is bolted, as indicated at 25 in Figure 3, to a metal lug 26 cast integrally with the cover of the casing. The upper conductor or support 24 is similarly secured to the neutral terminal M, as shown in Figures 3 and 4. Thus the valve member is supported in a very simple and practical manner and is readily accessible and may be easily removed and replaced.

It is to be understood that in all forms that the invention may take the parts, such, for instance, as the casings or other conducting portions, are properly insulated from the ground. The wooden poles, upon which the apparatus is frequently mounted, generally offer a sufficient margin of insulation to give adequate protection and insure proper operation of the apparatus.

In the event a surge occurs, such for example as lightning, the arc will strike across the spark gap 6 and l to the transformer casing and the current will pass through the valve material A to the ground indicated at El in Figure 1. In view of the fact that the valve material has a negative resistance characteristic, it is apparent that free discharge is afforded in this manner but nevertheless as soon as the surge ceases, the follow through current is prevented from flowing as a high resistance is interposed in this grounded circuit. Consequently the arc is stopped and the device resumes its normal func tioning.

With regard to the bird trouble, it is apparent that there is much less likelihood of a bird shorting across between the fingers t and i or between the finger i and the casing, due to the high resistance valve member A. However, if shortage should occur, it is obvious that the fault is immediately burned out and follow-through current is prevented, as in the case of a lightning surge.

If for any reason the live side of the transformer, that is to say, the high voltage primary, should become grounded on the casing, the valve material would have sufficient current to cause rapid heating and when this material gets hot, it becomes a good conductor and clinkers within a short time, thereby forming a conducting path and minimizing any possible hazard due to the transformer casing being connected to the high tension line and a difference of potential existing between the transformer case and the neutral conductor or ground. Continuous overload, if the live side were grounded to the easing inside of the fuse 8, would result in rupture sion lines and the casing.

of the fuse 8 and if the grounding of the live side to the casing occurred on the outer side of the fuse 8, the next line protecting device, for example that at the substation, would open.

It. will be seen, therefore, that this transformer can be used in a manner such that it does not require automatic auxiliary apparatus for its normal functioning but instead is self-contained and a complete and automatically actuating unit in itself.

The invention is equally applicable to a construction in which a plurality of gaps are employed.

For example, in Figure a double bushing transformer has been shown, the case 28 being connected through the valve member A to the ground as indicated at 29. The high tension lines 30 pass through the insulating bushings 3| and connect to the primary 32 of the transformer, fuses 33 being provided.

Although the fuses have been shown as in Figure 1, it is obvious that they may be positioned at any point desired both in the construction shown in Figure 5 and in Figure 1 between the transformer terminal or terminals and the high tension line or lines. The spark gaps 38 are provided between each high tension line 30 and the casing 28.

The secondary 34 has its neutral connected to the grounded neutral terminal 35 and the outer ends of the secondary are connected to the terminals 36. Suitable insulating bushings 31 are provided for the neutral and for the outer terminal conductors so that the secondary is insulated from the transformer casing 28.

In the form of the invention shown in Figure 6, the electrical instrumentality, such as a transformer, may have a portion of its casing formed of insulating material as indicated at 39 and may have a metal top or other metal portion indicated at 38. The spark. gaps M are positioned between the high tension lines 42 and the conducting portion 40 of the apparatus. The valve member A is connected between the ground 43 and the conducting portion 40 of the apparatus.

The invention is not limited to transformers as obviously, as shown in Figure 7, it could be applied to a switch oil immersed or otherwise. In this form of the invention the casing may be either made partly of insulating material and partly of conducting material as in Figure 6 or wholly of conducting material as shown in Figure l, the casing being indicated at 44. The high tension lines 45 extend into the casing and spark gaps it are positioned between such high ten- The casing is connected through the valve member to the ground ll.

Disconnect switches such as shown in Figure 8 are frequently mounted upon steel channel or other shaped supports 48 carried upon a pole 49. The disconnecting switch may be of any type, such, for instance, as one having the movable portion 50 and the stationary contact member 50 and being pivotally or otherwise supported from the conducting support 48. The live parts are insulated from the conducting portion 48 in accordance with the conventional practice. The line wires are indicated at 5| and spark gaps 52 are interposed between such line wires and the conducting portion 48. This conducting portion 48 is connected to the ground 53 through the valve member A.

The principle of this invention may be applied to the protection of high tension lines. For example, the high tension lines 54 as shown in Figure 9 may be supported by strings of insulating members 55 and arcing horns 58 and I! may be provided for each line. The arcing horns 56 are connected together and are connected through the valve member A to the ground 58. In this form oi the invention the conducting portion may be regarded as the arcing horns 51 and their common conductor 59 and this conducting member or portion is connected, as stated, through the valve member A to the ground.

It will be seen that this invention provides a novel means of protecting electrical instrumentalities in such a way that adequate and full protection is provided against lightning or other surges and that in the case of an instrumentality provided with a conducting portion dangerous voltages cannot build up between the instrumentality and the conducting portion, but when such a condition tends to occur, there is a relief across the spark gap and the surge is conducted to the ground, the valve member, however, preventing follow-through current.

It is to be noted that in the event a bird shorts across a spark gap, the fault is immediately burned out and follow-through current is prevented, as in the case of a lightning surge.

It is also to be noted that in the case of transformers whether of the single or double bushing type, it is impossible for high voltages to pass to the low voltage distribution system fed from the transformer.

It is also to be noted that the constructions whereby these results are obtained are very simpleand are cheap and easily produced and do not require elaborate or extensive parts.

- Although this invention has been-described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claim:

1. In an apparatus of the class described, an electrical device, a support therefor having a conducting portion, line wires leading to said device, spark gap means between at least one of said line wires and said conducting portion, and a valve member having one side connected to said conducting portion and having the other side grounded and forming a direct resistance path between said conducting portion and the ground, whereby the conducting portion is normally maintained at'ground potential and resistance to follow-through current is ofiered when an arc is established across said spark gap means.

2. In an apparatus or the class described, an electrical device, a support therefor having a 'conducting portion, line wires leading to said device, spark gap means between each of said line wires and said conducting portion, and a valve member having one side connected to said conducting portion and having the other side grounded and forming a direct resistance path between said conducting portion and the ground, whereby the conducting portion is normally maintained at ground potential and resistance to follow-through current is oflered when an arc is established acrosssaid spark gap means.

3. In an apparatus of the class described, an electrical device, a housing for said device, said housing having a conducting portion, line wires leading to said device, spark gap means between at least one line wire and said conducting portion, and a valve member having one side connected to said conducting portion and having the other side grounded and forming a direct resistance path between said conducting portion and the ground, whereby the conducting portion is normally maintained at ground potential and resist-- ance to follow-through current is offered when an arc is established across said spark gap means.

4. In an apparatus of the class described, an electrical device, a housing for said device, said housing having a conducting portion, line wires leading to said device, spark gap means between at least one line wire and said conducting portion, said apparatus having a grounded terminal, and a valve member connected between said grounded terminal and said conducting portion.

5. In an apparatus of the class described, an electrical device, a casing for said device having a conducting portion, line wires leading to said device, overload responsive, circuit interrupting means connected in series with said line wires for protecting said device, spark gap means interposed between at least one of said line wires and said conducting portion, and valve means having one side connected to said conducting portion and having the other side grounded, and forming a direct resistance path between said conducting portion and the ground, whereby the conducting portion is normally maintained at ground potential and resistance to follow-through current is ofiered when an arc is established across said spark gap means.

6.'In an apparatus of the class described, an

electrical device, a casing for said device having a conducting portion, said apparatus having a grounded terminal, line wires leading to said device, overload responsive, circuit interrupting means connected in series with said line wires ,for protecting said device, spark gap means interposed between at least one of said line wires and said conducting portion, and valve means having one side connected to said conducting portion and having the other side connected to said grounded terminal.

7. In an apparatus of the class described, an electrical device, a casing for said device having a conducting portion, line wires leading to said device, one of said line wires being grounded,

spark gap means interposed between the other line wire and the said conducting portion, and a valve member having one side grounded and having the other side connected to said conducting portion and forming a direct resistance path between said conducting portion and the ground, whereby the conducting portion is normally maintained at ground potential and resistance to follow-through current is offered when an arc is established across said spark gap means.

8. In an apparatus of the class described, an electrical device, a casing for said device having a conducting portion, line wires leading to said device, overload responsive, circuit interrupting means for protecting said device, spark gap means interposed between said conducting portion and each of said line wires, and a valve member having one side connected to said conducting portion and having the other side grounded and forming a direct resistance path between said conducting portion and the ground, whereby the conducting portion is normallymaintained at ground potential and resistance to 01- low-through current is oiIered when an arc is established across said spark gap means.

9. In an apparatus of the class described, a

transformer having a primary and a secondary,

former having a conducting portion, valve means interposed between said portion and the grounded side of said primary, and a spark gap between the live side of said, primary and said casing.

10. In an apparatus of the class described, a casing having a conducting portion, a transformer housed by said casing and having a live primary terminal and a grounded terminal, a secondary having a part thereof connected to said grounded terminal, and valve means interposed between said portion and said grounded terminal.

11. In an apparatus of the class described, a casing having a conducting portion, a live primary terminal and a grounded terminal, a transformer having a primary and a secondary, said primary having one side connected to said live primary terminal and the other side connected to said grounded terminal, a valve member connected between said portion and said grounded terminal, spark gap means between said casing and said live primary terminal, and overload responsive, circuit interrupting means connected in circuit with the live primary terminal.

12. In an apparatus of the class described, a casing having a conducting portion, a live primary terminal and a grounded terminal both carried by and insulated from said casing, a transformer housed by said casing and having a primary connected between the live primary term'nal and the grounded terminal, a secondary having a grounded neutral, a spark gap interposed between the live side of said primary and said casing, and valve means interposed between said portion and said grounded terminal.

13. In an apparatus of the class described, a casing having a conducting portion, a grounded vice housed within said casing, line wires leading to said electrical device, a spark gap interposed between at least one of said line wires and the conducting portion of said casing, and valve meansinterposed between the conducting portion of said casing and the grounded terminal, said valve means being removably held in place with reference to said casing.

14. In a device of the class described, a casing having a conducting portion, a transformer housed within said casing and having a primary and a secondary, line wires leading to said primary, spark gap means interposed between each of said line wires and the conducting portion of said casing, the secondary of said transformer having a grounded portion, and a valve member removably carried by said casing and having one side grounded and the other side connected to said conducting portion.

15. In an apparatus of the class described, a support having a conducting portion, an electric switch carried by said support, line wires leading to said electric switch, spark gap means interposed between at least one of said line wires and said conducting portion, and a valve member having one .side grounded and the other side connected to said conducting portion and forming a direct resistance path between said conducting portion and the ground, whereby the conducting portion is normally maintained at ground potential and resistance to follow-through current is offered when an arc is established across said spark gap means.

ROLLAND D. NELSON. 

